Subj : BINKP over TLS
To   : Alexey Fayans
From : Rob Swindell
Date : Fri Dec 20 2019 11:55 am

  Re: BINKP over TLS
  By: Alexey Fayans to Rob Swindell on Fri Dec 20 2019 09:09 pm

 > Hello Rob!
 >
 > On Fri, 20 Dec 2019 at 09:56 -0800, you wrote to me:
 >
 >  >> Isn't it your main argument against STARTTLS?
 >  RS> Under no case is Opportunistic TLS (e.g. STARTTLS) as secure as
 >  RS> Implicit TLS.
 >
 > So far you didn't provide a single fact proving that good STARTTLS
 > implementation is less secure than TLS on a dedicated port.

Opportunistic TLS gives both the client and the server (or a MitM) the ability to "opt-out" of using TLS. With an Implicit TLS session, no such option is availble; the entire TCP session is secure, or it doesn't exist.

 >  RS> Yes, the use of self-signed certs is less secure than
 >  RS> CA-signed certs, but that's a different matter and true for both
 >  RS> Opportunistic and Implicit TLS.
 >
 > Use of self-signed certs without a well-defined and implemented mandatory
 > mechanism to verify these certs (either trusted CA or any other similar way)
 > just turns whole security talk into a joke. Seriously.

A less funny joke than Binkd's CRYPT option. Seriously.

 >  >> Why not? It is perfectly mitigated and I explained that a few times
 >  >> already. You gotta stop looking back at old SMTP implementation
 >  >> that wasn't designed against active MitM attacks in the first
 >  >> place.
 >  RS> I look at all the applications of Opportunistic TLS and they're all
 >  RS> less secure than Implicit TLS.
 >
 > Examples?

NNTP, FTP, IRC.

 > Maybe you are just looking at bad / not suitable implementations.
 > Not all implementations are focused on MitM protection and that is fine,
 > similar to use of self-signed certs just to make it a bit harder to sniff
 > the traffic.

Security is a moving target. If you're going to implement something, as I have with binkps, you shoot for the state of the art, today's best practices, not yesterday's. STARTTLS is yesterday's solution to TCP session security and is being phased-out. It would be silly to implement STARTTLS in a newly-defined TCP applictaion protocol today.

                                            digital man

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